Explosive joints are frequently used in the aerospace and aircraft industries for attaching two structures together when such structures must be quickly separated during flight conditions. Explosive joints have the advantages of providing quick separation and high load carrying capability and of being highly reliable but relatively simple in structure and operation. There are, however, problems associated with the use of explosive joints. The major problem is that such joints generally produce high shock pulses during separation of the structures. These pulses can damage the avionics and adjacent hardware of the structures being separated.
A number of aproaches have been tried to alleviate the effects of the high shock pulses produced by explosive joints. One such approach is to position the avionics in a remote location. This approach usually results in a weight penalty and high density packaging of the avionics in the remote location. The high density packaging in turn causes cooling and access problems. The combination of the weight penalty and the cooling and access problems makes the remote location solution unacceptable in many situations.
Another approach is to provide shock isolation of the avionics; for example, by mounting the avionics package on rubber bushings. This approach is relatively effective but is difficult to design and expensive to carry out. The shock isolation system must be tested and analyzed for a wide range of temperatures. In addition, the system must be designed so that its natural frequency is not harmonic with the structure's frequency, and the appropriateness of the frequency again requires extensive and expensive testing the analysis.
A third approach is to provide shock attenuation within the structure itself. The major drawback to this approach is that in order to provide sufficient shock attenuation, it is necessary to increase the flexibility of the structure. Increasing the flexibility can result in a structure that is so flexible that there are significant stability and control problems.
Apparatus for explosively separating two structures or shattering or rupturing a structure or portion thereof is disclosed in each of the following U.S. Pats. Nos.: 3,135,163, granted June 2, 1964, to G. F. Mechlin, Jr., et al; 3,172,330, granted Mar. 9, 1965, to T. N. G. Lidmalm et al; 3,362,290, granted Jan. 9, 1968, to W. F. Carr et al; 3,453,960, granted July 8, 1969, to H. W. Qualls; 3,465,482, granted Sept. 9, 1969, to J. A. Chandler; 3,486,410, granted Dec. 30, 1969, to V. W. Drexelius et al; 3,505,925, granted Apr. 14, 1970, to W. F. Carr; 3,633,456, granted Jan. 11, 1972, to W. F. Carr et al; 3,698,281, granted Oct. 17, 1972, to O. E. Brandt et al; 4,137,848, granted Feb. 6, 1979, to D. Cunha; and 4,407,468, granted Oct. 4, 1983, to L. J. Bement et al.
Carr et al, U.S. Pat. No. 3,362,290, and Carr, U.S. Pat. No. 3,505,925, each disclose a system in which the products of an explosive charge are contained within a bellows that expands to move a piston to release two structures from each other. Qualls discloses an explosive charge inside a tube which expands upon detonation of the charge to sever a weakened portion of a skin of a structure to separate the structure into two parts. A system in which an explosive charge is detonated inside a flattened tube to expand the tube to a rounded configuration is disclosed by Drexelius et al in U.S. Pat. No. 3,486,410, Carr et al in U.S. Pat. No. 3,633,456, and Cunha in U.S. Pat. No. 4,137,848. In the Drexelius et al and Cunha systems, the expansion of the tube fractures a structure along a weakened line; and in the Carr et al system, the expansion of the tube moves a retaining pin against frictional forces.
Lidmalm et al disclose an end cone for a rocket missile pod carried by an airplane wing. The cone is jettisoned by explosively shattering it. This is accomplished by means of a plurality of spaced apart charges in the form of strips attached to the cone wall and placed between the laminations of the wall. When the charges are detonated, the wall is shattered into many small pieces, and the laminations also tend to be separated from each other. In one embodiment, the laminations are bonded together only at small spaced apart areas to facilitate separation of the laminations.
Chandler discloses a means for removing a protective plastic film from a heat radiator on a spacecraft. In one embodiment, the edge of the plastic film is molded into an elastomeric edge member that encircles the radiator surface and has a flat face which is bonded with a fairly brittle adhesive to the outer surface of the radiator. An explosive charge is molded within the geometric center of the elastomeric edge member and is detonated to expand the edge member in all directions. The expansion of the edge member breaks the adhesive bond and accelerates the edge member away from the radiator surface. The plastic film is pulled away from the spacecraft along with the edge member. In another embodiment, a flattened soft aluminum tube replaces the edge member, and a charge is detonated inside the tube to expand the tube to its original round cross section, to break the adhesive bond and pull the film away from the radiator as in the first embodiment.
Brandt et al disclose an explosive joint having a metal tube of oval cross section enclosed between two doublers. A core of two parallel explosive cords encased in a sheath of silicone rubber are positioned inside the tube. One or both of the explosive cords are detonated to expand the rubber sheath and tube into a round cross section to fracture the doublers along weakened portions formed by grooves or notches.
The known systems and the patents discussed above and the prior art that is discussed and/or cited in the patents should be studied for the purpose of putting the present invention into proper perspective relative to the prior art.